go_id,ontology,go_term,term_definition,evidence GO:0005102,MF,"receptor binding","Interacting selectively and non-covalently with one or more specific sites on a receptor molecule, a macromolecule that undergoes combination with a hormone, neurotransmitter, drug or intracellular messenger to initiate a change in cell function.",IPI GO:0005576,CC,"extracellular region","The space external to the outermost structure of a cell. For cells without external protective or external encapsulating structures this refers to space outside of the plasma membrane. This term covers the host cell environment outside an intracellular parasite.",IEA